LNG Plant Bridge (Metro Road) over Moonachie Creek
Borough of Carlstadt, Bergen County, NJ
Services Provided by AmerCom: Bridge Design, Roadway Design; Construction Support
Client: Williams Companies
As the prime consultant, AmerCom Corporation developed a unique design to completely replace this bridge on a private road in less than 2 weeks. This work for Williams included improvements of 0.10 miles of roadway and the construction of a new bridge at a cost of $2.6 million. All work was completed within the existing tight confines of 19’6” between two high pressure gas mains (30” and 36” in diameter). The existing 81-foot long by 18-foot wide two-girder bridge, was classified as functionally obsolete and structurally deficient. Since the bridge was low and spanned over a tidal waterway, the lower half of the girders were submerged twice a day during high tide, creating an ideal corrosive environment. The date of original construction was unknown and there had been modifications and maintenance improvements over the years.
Metro Road is a critical link to Williams’ LNG Plant serving as the primary access route. A winding secondary rutted dirt and gravel route serves as an emergency access route only. Use of this secondary route for an extended period of time was unfeasible for the heavy trucks servicing this plant. Since traditional construction methods would have taken a minimum of 4 to 6 months, ABC was selected as the only feasible alternative for construction. There was a two-week period during July when plant activity was relatively lower than the rest of the year and therefore AmerCom designed the bridge to be built within this construction window provided by the client. The design developed by AmerCom allowed the bridge to be demolished and constructed with a new substructure and superstructure to completion within 9 days under a full roadway closure. The additional days were for roadway and site construction.
Further compounding the challenges on the project besides the high pressure gas lines on either side of the proposed bridge were severe environmental constraints in the tidal waterway and surrounding area known as the Hackensack Meadowlands after the primary river flowing through it. The Meadowlands is a large ecosystem of wetlands in northeastern New Jersey that required NJDEP permitting. In order to simplify the permit process and cause as little disturbance as possible to the surrounding sensitive environmental area, the new structure maintained the existing waterway opening below the bridge and there was no work in the stream channel. The soft soils introduced geotechnical complexities that had to be resolved during design. and the cofferdam sheeting serve as a scour preventative measure for the new bridge.
The approach taken by AmerCom was to develop a design for ease of fabrication and rapid construction in a wet environment while giving a cost effective project within a constrained space. The proposed structure utilized precast abutment sections placed on steel H-Piles driven behind the existing abutments. Prefabricated superstructure units consisting of a precast concrete deck supported by twin steel built-up plate girders were placed on the new abutments. Precast approach and sleeper slabs were also used on a raised roadway profile of about 2’. The raised profile will eliminate the daily submergence of the steel girders. The bridge railing utilized anchor bolts protruding from the precast deck and the deck surface was overlain with PPC.
Continuous construction commenced on Friday, July 8th, 2016 at 7:00AM with the demolition of the existing superstructure and the bridge was available to vehicular traffic on July 22nd. Only site restoration and punchlist items remained.
Innovative techniques included:
• Segmental construction concept and sequencing in a narrow corridor;
• Design concept eliminated stream encroachment;
• Design concept minimize environmental permit process;
• Details for temporarily supporting new abutments allowing the superstructure to be built while the substructure concrete was still green;
• Moved the joints away from the bridge deck onto approaches;
• Deck and substructure closure pours using VES concrete.
• Deck overlain with Polyester Polymer Concrete
AmerCom provided construction support services during the round the clock construction. This is our second complete bridge replacement design project using ABC but the first one in wet conditions.